It provides some 20,000 heavy-duty bicycles, including hundreds at all the mainline stations.

For a minimum fee - less than £25 annually or less than £1 a day - commuters can pick up two wheels at automated rental points across the city.

When they have finished with the bikes they can drop them off at any rental point they like.

The scheme has become so popular that few bother with their own bicycles, which are often vandalised or stolen.

Paris city hall estimates that out of a population of two million in the centre of the city, only about 200,000 people actually own a bike, with up to 100,000 people a day instead relying on Vélib. "We are a very pro-bicycle city," said a city hall spokesman. "We want commuters to be able to use bikes easily and cheaply."

Mainline stations offer a huge amount of parking for bikes, usually metal stands on the pavements outside.

For those who want more security, there are lock-ups for around 250 bicycles at most of the larger stations.

Montparnasse station, for example, charges €5.30 (£4.50) for storing a bike for 24 hours. Gare du Nord, from where Eurostar trains head for London, charges €4.50 (£3.80) for the same service. Anyone who arrives at a station on their machine to find that the spaces are all taken is granted another 15 minutes of free rental time.

The terminals display information about neighbouring Vélib points including location, number of available bikes and spaces. Overnight, a fleet of 20 vehicles redistributes bicycles to high-demand stations in time for the next morning.

There were teething problems with the scheme when it started in 2007, with at least 3,000 bicycles stolen in the first year. Many were taken to eastern Europe and Africa while others were dumped. Some of the bikes also suffered mechanical problems.

But it has turned into one of the great success stories of the French capital. At first, 10,000 bicycles were introduced with 750 automated rental points, each with 15 or more bike spaces.

That number has now grown to 20,000 bicycles and 1,450 rental points - roughly one every 300 metres throughout the city centre.